Poly-p-Xylylenes, also known by their trade name of Parylene, are well known conformal coatings that are primarily used as insulators and isolators in electronics. These materials are interesting because of their ability to provide ultrathin films that conform to substrates of varied geometrical shapes and irregularities. Poly-p-Xylylenes are insoluble in every known organic solvent at room temperature and are tough, moisture resistant and impermeable to most gases and vapors. They have a stable temperature coefficient of capacitance that is independent of the temperature, and yet films remain tough and flexible at extremely low temperatures
Because Poly-p-Xylylenes are formed by vapor deposition polymerization, very thin, high quality pinhole free films of about 100 angstroms in thickness can be made with outstanding conformality and thickness uniformity. The film is firmly and contiguously bonded to a metallic substrate. Flexing does not separate these coatings from the metal. Bulk electrical properties are extremely stable with temperature and frequency while dielectric constants are unaffected by absorption of atmospheric water. Bulk resistivities are attractively high. All of these characteristics make this material very suitable as a dielectric for capacitor applications.
In some capacitor applications however, very high energy density storage capabilities are required. Therefore, a polymer with a very high dielectric constant is needed.